Department of Radiology, Stanford University, Stanford, California, USA.
Magn Reson Med. 2013 Aug;70(2):466-78. doi: 10.1002/mrm.24489. Epub 2012 Oct 5.
The main obstacle to high-resolution (<1.5 mm isotropic) 3D diffusion-weighted MRI is the differential motion-induced phase error from shot-to-shot. In this work, the phase error is addressed with a hybrid 3D navigator approach that corrects motion-induced phase in two ways. In the first, rigid-body motion is corrected for every shot. In the second, repeatable nonrigid-body pulsation is corrected for each portion of the cardiac cycle. These phase error corrections were implemented with a 3D diffusion-weighted steady- state free precession pulse sequence and were shown to mitigate signal dropouts caused by shot-to-shot phase inconsistencies compared to a standard gridding reconstruction in healthy volunteers. The proposed approach resulted in diffusion contrast more similar to the contrast observed in the reference echo-planer imaging scans than reconstruction of the same data without correction. Fractional anisotropy and Color fractional anisotropy maps generated with phase-corrected data were also shown to be more similar to echo-planer imaging reference scans than those generated without phase correction.
高分辨率（<1.5 毫米各向同性）3D 扩散加权 MRI 的主要障碍是来自 shot-to-shot 的差动脉动相位误差。在这项工作中，采用混合 3D 导航方法解决了相位误差问题，该方法通过两种方式校正运动引起的相位。在第一种方式中，针对每个 shot 校正刚体运动。在第二种方式中，针对心脏周期的每个部分校正可重复的非刚体脉动。这些相位误差校正使用 3D 扩散加权稳态自由进动脉冲序列实现，并在健康志愿者中与标准网格重建相比，显示出减轻了因 shot-to-shot 相位不一致而导致的信号丢失。与未经校正的数据重建相比，使用相位校正数据生成的扩散对比度更类似于参考回波平面成像扫描中观察到的对比度。相位校正后生成的分数各向异性和彩色分数各向异性图也比未经相位校正生成的图更类似于回波平面成像参考扫描。
